crypto/tls: add FreeBSD root certificate location     Fixes issue 2721.
crypto/tls: add FreeBSD root certificate location
    Fixes issue 2721.

R=golang-dev, bradfitz
CC=golang-dev
http://codereview.appspot.com/5532090

Committer: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go